The Flow Cytometry Core will meet the special needs of the Program Project members. The[unreadable] availability of quality sorting and analysis capabilities is essential for the success of the research[unreadable] efforts proposed in this Program Project Grant. We will be active users of both the MoFlo cell[unreadable] sorting and LSR II fluorescence analyzer in the studies dealing with: sorting of small numbers of[unreadable] cells based on either cell surface or transduced gene markers; and multiparameter analyses to[unreadable] detect biochemical and biological changes in rare populations of lymphocytes as well as whole[unreadable] populations transduced with various genes. In many cases, the individual program directors will[unreadable] need access to machines that will require triple or even quadruple staining for the sophisticated[unreadable] experiments outlined in the proposal. The specific aims of this core are 1. To provide high speed[unreadable] cell sorting to isolate cells that can be used for functional and biochemical studies; 2. To provide[unreadable] analytical flow cytometry using a state-of-the-art LSR II to perform multiparameter analyses and[unreadable] 3. To provide innovative approaches to study immune tolerance using flow microscopy. The[unreadable] availability of the core ensures that the PPG investigators will have access to this essential[unreadable] facility on the UCSF campus.